A small squeeze reveals new clues about an unusual kind of magnet

Researchers at Rice University discovered that gently squeezing a crystal of iron sulfide simultaneously affects two of its unusual properties: its magnetic signal and how electricity flows through it. This finding provides a better understanding of how a new class of magnetic materials called altermagnets work and offers a straightforward method to control their behavior.

Altermagnets are intriguing because they combine features of two well-known magnets - they have minimal overall magnetism but still influence moving electrons in unique ways that could benefit future electronic devices. The Rice team examined a hexagonal form of iron sulfide, or FeS, which has a very small residual magnetic moment and produces an unusual electrical signal known as the anomalous Hall effect.

When the crystal is squeezed in one direction, both the magnetic signal and electrical signal weaken together, indicating a close connection between the two effects. To study this relationship, the researchers used neutron beams at Oak Ridge National Laboratory to analyze the material's magnetic arrangement. They found that while the basic magnetic structure remains unchanged, the squeeze alters which magnetic orientations are most common inside the crystal.

This makes FeS particularly responsive to mechanical tuning. The experiments also shed light on why FeS generates its anomalous Hall effect, suggesting that the electrical signal changes in tandem with the material's tiny magnetic moment, pointing to a shared underlying physics. Controlling these properties with mechanical strain could lead to advancements in spintronics, a field focused on using the magnetic properties of electrons for information storage and processing.

Such devices could potentially operate more efficiently with less magnetic interference and lower energy consumption compared to current technologies.